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In 1978, Daniel B. Kopans, MD, was appointed head of the Xeroradiography Division at Massachusetts General Hospital. In addition to other soft tissue imaging, the division performed mammograms for eight women each day (2,000 each year) using the xeroradiographic technique. Mammography screening was in its infancy, but Dr. Kopans helped to develop this new field of "Breast Imaging" (1). The Division of Breast Imaging at Mass General now cares for more than 35,000 women each year and has led the development of Breast Imaging as a radiologic sub-specialty.
Since the inception of mammography, the ability to detect breast cancer on 2-dimensional (2D) mammograms has been compromised by superimposed normal breast tissues hiding many small cancers. The standard mammogram is like a book with clear pages. You can hold the book up to the light and look through it, but the words are superimposed one on the other making it difficult to read.
Dr. Kopans sought a way to look at each page, individually, to allow radiologists to uncover hidden cancers. Computed tomography and other methods to accomplish this require high doses of radiation. In 1978, reading about a technique called tomosynthesis, Dr. Kopans realized that this could be the solution to the problem. A few low dose x-ray images taken from different directions would allow him to synthesize as many "pages" through the breast as were needed. Unfortunately, he had to wait almost 15 years for the development of digital detectors and computers powerful enough to enable breast imaging using tomosynthesis.
In 1992, while helping to develop digital detectors for mammography, Dr. Kopans set a goal for the Mass General Division of Breast Imaging to develop tomosynthesis of the breast. In 1996, Mass General physicist Loren Niklason, PhD, Laura E. Niklason, MD, PhD and Dr. Kopans filed a patent entitled "Tomosynthesis System for Breast Imaging," which described a digital breast tomosynthesis (DBT) system that collected digital images from X-rays passing through the breast from a tube that moved above the breast (2). These DBT projection images from the system allowed the creation of the "pages" through the breast that Dr. Kopans had envisioned. The patent was approved in 1999 (#5872828). Obtaining a grant from the U.S. Department of Defense, Mass General sub-contracted to General Electric to build the first DBT prototype.
Using the this prototype, the Mass General team obtained a whole breast DBT study of the first volunteer in 1999. To our knowledge, this was the first DBT exam ever acquired. Subsequent research at Mass General involving thousands of additional volunteers showed that DBT could find cancers that were not visible on standard 2D mammography (Figure 1). As a further benefit, because it eliminated the superposition of normal tissues that could simulate a cancer, DBT also reduced the "false positive" recall rate (3,4). Mass General subsequently licensed the DBT patent to General Electric.
Mammography screening was introduced in the US in the mid-1980s. Owing to earlier detection and improvements in therapy, the death rate from breast cancer began to fall in 1990 for the first time in 50 years (5,6). There are now 35% fewer women who die each year from breast cancer than would have died had screening not been introduced (7,8,9,10,11,12,13,14,15,16,17,18,19,20).
Therapy has improved, but the most lives are saved when breast cancers are treated earlier. Recognizing that 2D mammography was not the ultimate answer to detecting breast cancer, Dr. Kopans pursued DBT as a major improvement. Numerous studies have now shown that DBT can find more small breast cancers that are missed on standard 2D mammography (21,22,23,24,25,26,27,28,29,30) while reducing the recall rate from screening (3,4,31,32,33,34).
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